Doctrine Collections

Doctrine Collections is a library that contains classes for working with arrays of data. Doctrine Collections provides an interface named Doctrine\Common\Collections\Collection that resembles the nature of a regular PHP array. That is, it is essentially an ordered map that can also be used like a list. A Collection has an internal iterator just like a PHP array. In addition, a Collection can be iterated with external iterators, which is preferable. To use an external iterator simply use the foreach language construct to iterate over the collection, which calls getIterator() internally, or explicitly retrieve an iterator though getIterator() which can then be used to iterate over the collection. You can not rely on the internal iterator of the collection being at a certain position unless you explicitly positioned it before.